The slurry supplying device in a wet blasting system is used to feed a pressurized slurry (a mixture of solid particles and liquid, mixed in a selected weight ratio) to the blasting gun in said system. For example, referring to attached FIG. 5, Japanese Patent SHO-29 (1954)-3046 discloses a system in which slurry agitation device B is installed at the bottom of a slurry storage tank A. The agitation device B has a shell E of hollow, substantially hemispherical shape, or inverted cup shape, and has a passage D for air flow connected to an air introducing duct C. The agitation device B is submerged in the slurry. A nozzle H, which has air blowing holes G, intersects the air flow tube D and extends at a right angle thereto. Compressed air sent via air introducing duct C is blown out through the air blow holes G and the tube D. The abrasive particles and liquid are agitated and well mixed by the air that is blown from the nozzle H into the slurry. The well-mixed slurry is sent to the blasting gun (not shown) through a slurry supply pipe I.
In the prior art device mentioned in the preceding paragraph, the abrasive particles settle on the bottom of the slurry reservoir and in the slurry circuit when operation of the apparatus is stopped. This presents a difficult problem, when restarting the apparatus, because it is necessary to re-suspend, in the liquid, the solid abrasive particles which may be cohered to each other, for example, when said abrasive particles have a high density or exhibit a cohesive nature. When abrasive particles having a relatively low density (for instance, a specific gravity of 1.0-2.0) or a small particle size (for instance, a mean particle diameter of 50-0.5 .mu.m) are blasted by a wet blasting machine of the pressure vessel type, the slurry blasted from the blasting gun should be in a well mixed state. This condition is necessary if the object to be blasted has a low hardness or the object must be finished with a uniform surface roughness. Examples of industries in which such a uniformly finished surface is desired are the electronic industry, the finishing or cleaning of dirt from lead frames, the surface preparation of surfaces before P.V.D. or C.V.D., etc.
Adjustment of the operational conditions to meet the requirements of the industries mentioned above is difficult in conventional wet blasting apparatuses because conventional apparatuses are not designed or manufactured to provide the operational conditions necessary to finish the objects to be blasted, using low density particles or particles of very small mean diameter, and using a low blasting pressure.
It is an object of this invention to provide a slurry supplying device in a wet blasting system, in which a uniformly mixed slurry can be obtained easily and no danger exists that the particles will settle on the bottom of the slurry reservoir and in the piping system after the blasting operation has ended.